PSI - Issue 43

Zuzana Molčanová et al. / Procedia Structural Integrity 43 (2023) 89– 94 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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3. Results and discussion 3.1. Microstructure

b.

c.

a.

Fig. 2. a. Microstructure of the bimetal in region close to the joint a. in as-prepared state b. after heat treatment OC1 c. after heat treatment OC2 . Magnification 1000x, light region (top) is Alloy 625, darker region (below) is Ferritic steel. Fig. 2. shows microstructures of the Alloy 625/ P355NH bimetal at their joint of the as-prepared state, as well as after the OC1 and OC2 heat treatments. The microstructure of the Alloy 625 (upper light region) shows in all cases elongated grains of size  10  m having orientations which copy the wavy shape of the joint. On the other hand, at the joint there are visible equiaxial grains resulting from high plastic deformation followed by thermally induced recrystallization. Micrographs also show the presence of small cracks and cavities (of sizes below 20  m) which can be attributed to imperfect bonding and/or extensive residual stresses. 3.2. Phase composition

Fig. 3. XRD patterns taken from a different part of the Alloy 625-P355NH bimetal after the heat treatment OC2 .